A floating magnetic head of the composite type which has been heretofore frequently used is generally indicated by reference numeral 1 in FIG. 5. This head 1 has a substantially rectangular slider 2 made of a ceramic such as calcium titanate. Rails 3 and 4 for producing a floating force are mounted on the top surface of the slider 2 which is opposite to a magnetic recording medium. One rail 3 has a slit 6 of a given depth, the slit 6 extending longitudinally of the rail 3 on the side of its trailing end 5 at which the medium exits from the head. A head core 8 having a read/write gap 7 and made of a ferromagnetic substance such as a ferrite is inserted in the slit 6. The core 8 is rigidly mounted by sealing of glass or other bonding material.
A groove 10 which increases gradually in depth from its leading end 9 toward its trailing end 5 is formed at one corner of the slider 2. The groove 10 extends to the trailing end 5. The head core 8 has a leg 8a mounted in the groove 10 on the side of the trailing end 5. A coil 11 is wound around the leg 8a of the core.
In this floating magnetic head 1, the coil 11 is wound only on the core leg 8a disposed on the side of the trailing end 5. Therefore, if an external magnetic field which is perpendicular to the floating surfaces of the rails 3 and 4 acts on the floating surfaces, an electromotive force may be induced in the coil 11, whereby noise is produced.
It is sometimes necessary that the coil 11 is composed of a number of turns. In this case, the coil 11 is required to form multiplex winding because the width of the groove 10 is limited. However, where the coil 11 is built in multiplex winding, the outer portion of the coil 11 is inferior in sensitivity to the inner portion. Also, there is the possibility that the outer portion of the coil 11 is disarranged toward the rail 3 and makes contact with the magnetic recording medium, thus creating a breakage.
The present applicant in U.S. patent application Ser. No. 08/059,297 has already proposed an improved floating magnetic head to alleviate the foregoing problems. This head is generally indicated by numeral 1 in FIG. 6. It is to be noted that like components are indicated by like reference numerals in various figures. In FIG. 6, the head 1 has a head core 21 provided with a read/write gap 20. The core 21 has two legs 21a and 2lb which are located on the side of the entrance end 9 and on the side of the trailing end 5, respectively, of the groove 10. Coils 22 and 23 having the same number of turns are wound around the legs 21a and 21b, respectively, of the core.
In this floating magnetic head 1 shown in FIG. 6, when it undergoes an external magnetic field, the coil 22 wound on the core leg 21a on the side of the leading end 9 and the coil 23 wound on the core leg 21b on the side of the trailing end 5 cancel out the induced electromotive force. Thus, generation of noise is suppressed. Also, it follows that one coil is divided into the two equal coils 22 and 23 wound around the legs 21a and 21b, respectively. The number of turns of each of the coils 22 and 23 is reduced accordingly. This reduces the amount of lap winding to thereby prevent deterioration of the sensitivity. Hence, breakage of the coils due to disarrangement of the coils is prevented.
In the floating magnetic head 1 shown in FIG. 6, the groove 10 is formed obliquely such that its depth gradually increases from the leading end 9 toward the trailing end 5. The clearance L.sub.1 (see FIG. 2; the core leg 30a on the side of the entrance end shown in FIG. 2 corresponds to the core leg 21a on the side of the leading end 9) between the core leg 21a on the side of the leading end 9 and the bottom 24 of the groove is different from the clearance L.sub.2 (see FIG. 2; the core leg 30b on the side of the exit end shown in FIG. 2 corresponds to the core leg 21b on the side of the entrance end 9) between the core leg 21b on the side of the trailing end 5 and the bottom 24 of the groove. Consequently, the amount of the coil 22 wound around the core leg 21a on the side of the leading end 9 differs from the amount of the coil 23 wound around the core leg 21b on the side of the trailing end 5.
As shown in FIG. 6, in order to wind the equal amounts of the coils 22 and 23 on the core legs 21a and 21b, the groove 10 is made deeper more than needed. This may increase the amount of overhang of the rail 3 located over the groove 10, thus deteriorating the flatness of the rail 3. Where the coil 22 is wound around the core leg 21a on the side of the leading end 9, the winding operation is more difficult to perform than on the side of the trailing end 5 due to the interference with the bottom 24 of the groove. Also, a larger amount of work is needed.